We report a metal-organic framework-derived Co9S8 nanoflakes on reduced graphene oxide sheet composites as an advanced sodium-ion battery anode. Using a galvanostatic intermittent titration technique, we reveal that the sodium diffusion coefficient of the composite is higher than that of its counterpart. Ex-situ scanning electron microscopy images suggest the excellent mechanical stability of Co9S8 nanoflakes on the reduced graphene oxide sheet electrode during cycling, thereby facilitating cyclic stability. The partial surface-induced capacitive effect also contributes to electrochemical performance. With the reduced graphene oxide, the Co9S8 nanoflakes on the reduced graphene oxide sheet electrode deliver a high discharge capacity of 551 mA h g-1 at 0.1 A g-1, a good rate capability at 10 A g-1, and an excellent cyclic stability up to 500 cycles. rGO/Co9S8 shows potential for practical applications in Na3V2(PO4)3‖rGO/Co9S8 full cells.
Keywords: Ion diffusion coefficients; Long-term stability; Metal organic frameworks; Sodium ion battery; Transition metal sulfides.
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